尿液血幼素及丙二醛濃度與貓慢性腎病進程之相關性

Abstract

在多種腎臟疾病中，鐵代謝的失衡，是造成腎臟疾病惡化的因子。鐵透過多種途 徑傷害腎臟組織，其中，氧化壓力是最主要的途徑之一;與鐵堆積及脂質氧化高度 相關的鐵依賴性細胞凋亡(ferroptosis)，也已證實與人類和大鼠的腎損傷密切相關。 Hemojuvelin 是身體調控鐵平衡的重要因子，其尿中濃度可作為人類急性腎衰竭的 早期指標，而慢性腎病的貓其尿中 hemojuvelin 濃度也顯著高於健康者。在大鼠的 實驗模型中，腎臟細胞 hemojuvelin 的調控，與腎臟的鐵堆積及組織傷害相關;急 性腎損傷會導致腎臟 hemojuvelin 的表現上升，而抑制 hemojuvelin 的切割，則可 降低腎臟組織的鐵堆積、並降低腎臟組織的受損程度。然而尿液中的 hemojuvelin 與腎臟氧化壓力的關聯性，以及兩者與貓慢性腎病進程的關聯，目前尚未有相關數 據可供參考。 本研究回溯性納入了 2018 一月至 2021 十一月，於台大動物醫院就診的 60 隻慢 性腎病貓。並分別以酵素結合免疫吸附分析法(ELISA)，測定其尿中 hemojuvelin 濃 度;硫代巴比妥酸反應測試搭配高效液相層析法(HPLC)，測定其尿中脂質氧化指 標—malondialdehyde 濃度。兩者皆以尿中肌酸酐濃度作為校正基準，分別得 urine hemojuvelin-to-creatinine ratio (UHCR)及 urine malondialdehyde-to-creatinine ratio (UMCR)。 實驗結果顯示 UHCR 與慢性腎病的惡化顯著相關。90 天內發生慢性腎病惡化者 有顯著較高的 UHCR(中位數 54.42 [IQR 25.31, 97.96] *10^-7 vs. 15.89 [IQR 5.58, 39.55] *10^-7，p=0.009)。ROC 曲線分析顯示，UHCR 預測 90 天內惡化的最佳臨界值為 47.744*10^-7;在此臨界值下，預測 90 天內惡化的敏感性及特異性分別為 0.611 和 0.867。以此臨界值為分界，K-M 生存分析顯示 UHCR 較高者，其惡化期間顯著 較短(中位數 81 [95% CI, 40-122]天 vs. 556 [95% CI, 246-866]天，p<0.001)。Cox regression analysis 同樣顯示高 UHCR 者有較高的惡化風險(HR 4.337 [95% CI, 1.971-9.545]，p<0.001)，且此風險獨立於傳統的腎指標。此外，在線性迴歸模型下， UHCR 與 UMCR 顯著相關，此相關獨立於傳統的腎指標、但與較高的 globulin 有 關。然而，UMCR 與慢性腎病惡化間未能發現關聯。 總結來說，UHCR 具有預測貓慢性腎病惡化的潛力，雖然 UMCR 未和病程惡化顯 著相關。同時，UHCR 與 UMCR 二者的顯著關聯性，顯示 UHCR 的升高與相關的 鐵代謝失衡，與脂質氧化相關。

Iron dysregulation contributes to multiple types of renal diseases. Iron causes damage to kidneys through several pathways, and many of them related to increased oxidative stress. Specifically, the iron-dependent cell death, known as ferroptosis, is featured by iron accumulation and lipid peroxidation. Ferroptosis is known to correlate closely to kidney injury in human and rats. Hemojuvelin (Hjv), an iron-regulating protein, is shown to be a promising early biomarker for human acute kidney injury (AKI). Meanwhile, the urinary concentration of Hjv elevated significantly in cats with chronic kidney disease (CKD). Regulation of renal cells’ Hjv is related to iron accumulation and tissue injury in rats’ model. AKI led to Hjv upregulation in kidney tissues, while inhibiting Hjv cleavage can reduce renal injury significantly. However, the relation between urinary Hjv and renal oxidative stress, as well as their relation with CKD progression, has not yet been investigated in feline CKD. We retrospectively included 60 client-own CKD cats, presented to NTUVH during January 2018 to November 2021. Urinary Hjv concentration was measured by commercial enzyme-linked immunosorbent assay (ELISA) kit. Renal oxidative status was evaluated through urinary malondialdehyde (MDA) concentration, which was measured by thiobarbituric acid reactive substances (TBARS) assay combined with high performance liquid chromatography (HPLC). Both concentrations will be normalized by urine creatinine concentration (urine Hjv-to-creatinine ratio, UHCR; urine MDA-to- creatinine ratio, UMCR). Our results showed a significant correlation between UHCR and feline CKD progression. Those who progressed within 90 days have significantly higher UHCR (median [IQR], 54.42 [25.31, 97.96] *10^-7 vs. 15.89 [5.58, 39.55] *10^-7; p=0.009). ROC analysis showed the best cut-off for UHCR prediction of 90-day progression was 47.744*10^-7, with sensitivity and specificity of 0.611 and 0.867, respectively. When divided by this cut-off, K-M survival analysis showed a significantly shorter progression-free interval for those with higher UHCR (median [96% CI], 81 [40-122] days vs. 556 [246-866 days], p<0.001). Similarly, Cox regression analysis also showed an increased HR for progression in those with higher UHCR (HR 4.337, 95% CI 1.971-9.545; p<0.001), which was independent of tradition renal indexes i.e., sCrea and BUN. UHCR was found significantly correlated with UMCR, which was independent of traditional renal indexes but dependent on serum globulin. There was no significant correlation between UMCR and CKD progression. To sum up, UHCR predicts CKD progression in cats. On the other hand, no correlation was found between UMCR and feline CKD progression. UHCR correlates significantly with UMCR, indicating UHCR and related iron dysregulation may correlates with lipid oxidation.